soundwire: qcom: Constify static structs

soundwire: qcom: Constify static structs

qcom_swrm_port_ops and qcom_swrm_ops are not modified and can be made
const to allow the compiler to put them in read-only memory.

Before:
   text    data     bss     dec     hex filename
  18266    3056     256   21578    544a drivers/soundwire/qcom.o

After:
   text    data     bss     dec     hex filename
  18426    2896     256   21578    544a drivers/soundwire/qcom.o

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20200609230029.69802-1-rikard.falkeborn@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>